Optenet announced that "In France, Internet access providers are legally required to provide, free of charge to all its customers, filtering solutions directed at the protection of children .. OPTENET, has secured more than 70% of home filtering market in the country .. The latest companies to acquire OPTENET’s PC WebFilter are Virgin Mobile and Coriolis".
Both operators are MVNOs - Virgin over Orange and Coriolis over SFR.
See "In France, Optenet’s technology is available through several providers for about 70% of Internet users across the country.' - here.